1.1 Field of the Invention
The present invention relates to electrochemical devices, and, more specifically, to electrochemically-powered devices. Still more specifically, the present invention relates to electrochemically -powered timing devices. The invention has applications in the areas of time keeping and alarms.
1.2 The Related Art
Many aspects of our modem economy require managing ephemeral items. Goods such as foodstuffs have only a limited shelf-life before they become unsaleable or rancid. Substances such as blood can be placed in storage for only a relatively short time before becoming unusable. Files may contain information that is time-sensitive or hold papers that must be acted upon before the expiration of a specified period. The availability of a service or resource, such as access to the Internet or a parking stall, may be regulated or charged in terms of fixed chronological periods.
In each case noted above, there is a requirement of time management. In some cases this is performed by marking an item, e.g., with a "Sell By", "Use By", or "Process By" date that must be compared, usually manually, with the current date to determine availability or priority. In other cases, a meter, such as a stopwatch or countdown timer, is used to regulate charges or access. In general, however, the efforts required to manage time-sensitive items require a great deal of manual labor as some chronological indicator, such as a time stamp, must be read and compared to the current time before a determination of whether the time period in question has expired can be made.
In addition, the use of a fixed time period may be arbitrary and only crudely related to the relevant time period. For example, the rate at which foodstuffs spoil is a function of several variables, including temperature and humidity. However, present technology cannot provide freshness indicators sophisticated enough to account for such factors. Instead, a fixed period is provided for the sale of perishables even though that period may be suboptimal and lead to the needless destruction of great quantities of food.
Thus, technologies that can ease the determination of the expiration of a fixed time period have great practical utility. However, the application of current time keeping technologies such as electronic timers or alarms to the maintenance of goods sold in bulk or regulating access to services or resources is often cost prohibitive and/or cumbersome. For example, the construction of electronic devices for warning of the expiration of a time period requires various components and portable power sources that are relatively expensive to fabricate and assemble. Such devices also would likely be too bulky for the application to mass-produced goods perishables such as meat and dairy products. In addition, these devices cannot vary the rate of timing to account for external variables.
Thus, there is a need for a chronological device that is inexpensive to assemble, compact, lightweight, and provides a relatively succinct indication of the expiration of a time period. In addition, in some cases it would be preferable to provide timers that can also reflect ambient conditions such as temperature and humidity. The present invention meets these and other needs.